The purpose of the present study is to pilot test a 12-week intensive lifestyle program for adolescents with overweight and T1D utilizing group exercise classes from Bright Bodies adapted for this population, supplemented with coping skills training and diabetes self-management education to address problem solving behaviors that limit their physical activity and weight control. Our primary aim is to evaluate the changes in physical activity adherence, anthropometrics (body mass index percentile for age, body fat percentage), and self-management behaviors following this 12-week lifestyles program among sedentary adolescents with T1D and overweight (n=25, OW) compared with sedentary adolescents with T1D and normal weight (n=25, NW). We hypothesize that the OW group will achieve improve physical activity adherence and anthropometrics to the same or greater extent as the NW group and previous Bright Bodies cohorts, and that these changes will correlate with improved exercise-related problem solving.